Balanced mixers have utilized mixer diode pairs mounted in a variety of configurations in or adjacent to several different types of wave propagating structures. Utilization of these diode pairs to mix local oscillator and incoming RF input signals and to generate sum and difference IF signal currents therein is generally well known in the art and is described, for example, in U.S. Pat. Nos. 3,584,306 and 3,638,126. Similar techniques are also described in a publication by M. V. Schneider et al entitled "Strip Line Down Converter With Sub-Harmonic Pumping," Bell System Technical Journal, Vol. 53, pages 1179-1183, July-Aug. 1974.
In recent years, the increased interest in the millimeter wave frequency and wavelength range (30-300 GHz) of the electromagnetic frequency spectrum and particularly the interest in certain useful frequency transmission "windows" therein have precipitated a corresponding and continuing size reduction in the waveguide structures used for propagating these millimeter waves. One of these transmission windows of interest is at 140 GHz, and using the conventional reduced height waveguide structures for a typical mixer wafer mount, the corresponding waveguide size would be approximately 0.065 inches wide and approximately 0.0065 inches high. Although the mounting of mixer diodes within these very small dimensions could probably be accomplished, such dimensions correspond to the upper frequency limit for the normal conventional honeycomb diode whisker mount configurations.
Therefore, it is manifestly desirable to provide a balanced mixer-in-waveguide structure which is capable of mixing frequencies out to 300 GHz or higher, but which does not, of necessity, require corresponding further reductions in waveguide size relative to the above dimensions.